Heating apparatus



Jan. 21, 1941. c M s 2,229,032

HEATING APPARATUS Filed Nov. 23, 1938 2 Sheets-Sheet l M ii i ii I i l3% 1 1 l 1! E i F- INVENTOR CARLYLE M. AsHLEY BYM ATTORNEY Jan. 21,1941. c. M. ASHLEY \HEATING APPARATUS Filed Nov. 25, 1938 2 Sheets-Sheet2 IRIJIIIAUIIIIIMII INVENTOR Chane-Miami! BY ?f g ATTORNEY Patented Jan.21, 1941 UNITED STATES PATENT OFFICE Carrier Corporation, Syracuse,

poration of Delaware N. Y., a cor- Application November 23, 1938, SerialNo. 241,906

2 Claims.

- This invention relates to heat exchange apparatus, and moreparticularly to heat exchange apparatus of the type in which a fluidsuch as steam is utilized to heat a fluid such as air.

The general object of the invention is to provide an improved device forheating air or the like by heat exchange with steam or similar fluid, inwhich freezing due to low temperatures of the entering air iseffectively prevented.

In various types of air heaters heretofore known, the efficiency of theheaters has been considerably reduced by the presence in the heaters ofquantitles of air locked therein. Efficiency losses of '15% or more dueto such air-binding have not been uncommon. It is an object of thepresent invention to substantially completely eliminate air-binding, toinsure a relatively high heat transfer efficiency.

It is another object of the invention to provide an improved air heaterparticularly well adapted to be installed in duct-work or the likecomprising a part of an air conditioning or ventilating system.

It is another object of the invention to provide a heating apparatus inwhich the supply of heating medium such as steam may be throttled, ifdesired, without danger of freezing condensate resulting from cooling ofthe steam, and with the assurance that all portions of the air streamcontacting the heater will be tempered substantially uniformly.

Still another object of the invention is to provide a steam heatingdevice for heating air or the like which is relatively simple andinexpensive to construct, and which is highly reliable and effective inoperation.

A feature of the invention resides in the provision of an apparatus forheating air or the like by means of steam or the like, which comprises aplurality of outer tubes each containing an inner tube provided with aseries of orifices spaced intermediate the extremities of the innertube, each inner tube being spaced from its surrounding outer tube,steam being supplied to each inner tube and condensate being withdrawnfrom each outer tube at the same side of the apparatus.

- Another feature of the invention resides in the provision of an airheating apparatus as referred to in the preceding paragraph in whichsteam passing through the oriflces formed in each inner tube isdischarged back toward the steam inlet end of the apparatus through aplurality of tend to be trapped therein, thus to prevent airbinding ofthe apparatus.

Another feature of the invention resides in the provision of anapparatus as referred to above, in which the steam supply header andcondensate return header are at the same side of the apparatus, and inwhich the fluid in said supply header is in heat exchange relation withfluid in said return header.

Another feature of the invention resides in the provision of a headerstructure comprising a steam supply portion and a condensate returnportion, both of said portions forming part of an integral structure andbeing separated by a partition adapted to promote heat exchange betweenfluids contained in said respective portions.

Other objects, features and advantages of the invention will be moreapparent from the following description, to be read in connection withthe accompanying drawings in which:

Fig. 1 is a side elevational view, partly in section, of a heatingapparatus embodying the invention in a preferred form;

Fig. 2 is an end elevational view of the structure of Fig. 1, partlybroken away, and with a portion of the surrounding casing removed;

Fig. 3 is a view, in section, taken on the line 3-3 of Fig. 1;

Fig. 4 is a view similar to Fig. 3, of a modified form of the invention;

Fig. 5 is a fragmentary detail view, taken on the line 5-5 of Fig. 3,and

Fig. 6 is a fragmentary detail view, taken on the line 66 of Fig. 4.

Referring to the drawings, the numeral Ill designates the end wall of acasing structure including top wall II, a second end wall l2, and abottom wall l3. The casing thus formed is generally of rectangularshape, and is relatively shallow. The casing may be so positioned in anair duct or the like, that the top wall II and bottom wall l2 aresubstantially horizontal and so that air flows through the casing insubstantially horizontal direction, as indicated generally by arrows I4in Fig. 2. However, the heater may also be used advantageously in avariety of other positions permitting the return of condensate bygravity.

Suitably mounted within the outer casing, as by bolts IE or in any otherdesired manner, is a header structure generally designated I6, situateadjacent the end wall I I. Header structure I6 is preferably shrouded bycasing plates I1, so that it is protected from direct contact with theair or other gas to be heated which is caused to flow through the casingunder the influence of a fan or the like.

The header structure I6 includes a partition IIa which is preferablycast orotherwise formed integral with the outer portion of the headerstructure, and which is formed of any suitable material having arelatively high heat conductivity. Partition I'Ia extends substantiallythroughout the length of' the header structure, thus providing an inletheader I8 for steam or similar heating medium and a return header I9 forcondensate. Inlet header I8 is provided with an inlet connection throughwhich steam is supplied to header I8, and header I9 is provided with areturn connection 2I, through which condensate may be drained therefrom.

Extending outwardly from the header I8 through suitable openings formedin partition Ila are a plurality of steam tubes 22, each steam tubebeing positioned within an outer or return tube 23 which is receivedwithin an extension 24 of the header structure and which communicateswith return header I9. Each outer tube extends throughout the length ofthe outer casing and extends through openings 25 formed in the end wallI2, which constitutes, in effect, a tube sheet supporting the outertubes. The far end of each outer tube is sealed, as by plugs 22. Theouter tubes are approximately horizontally disposed one above the other,but are inclined downwardly toward the return header I9 at a slightangle to promote the return of condensate, by gravity, to the returnheader I9.- The outer tubes 23 are provided with extended surface,generally designatcd 21, of any desired type, such as spiral fins, topromote heat transfer from the tubes to air passing through the heater.

The inner tubes 22 extend substantially completely throughout the lengthof the outer tubes 23 and are preferably concentric therewith. The farends of the inner tubes 23 are preferably closed, but the tubes areprovided with a plurality of apertures or orifices 28 spaced lengthwiseof the tubes and preferably arranged peripherally therearound. Theseorifices serve to deliver steam from within the inner tubes 22 into theannular spaces between the inner tubes and the outer tubes. Preferablythe orifices 28 are provided with nozzle or deflector formationsarranged to discharge the steam delivered from within the tubes 22 backtoward return header I 9 at relatively high velocity. While any desirednozzle or deflector arrangement may be used, it is preferred to formthese by punching out portions of the inner tubes 22, as indicated at29, whereby the orifices 28 and nozzle discharge formations may readilybe provided in a single simple operation. The nozzle formations 23 mayserve, if desired, as spacer members for maintaining the inner tubes 22in desired spaced relationship with the surrounding tubes 23. Due to themanner in which steam is discharged from within the inner tubes, thereoccurs an ejector action whereby the steam tends to entrain any airwhich may be in the tubes of the heater. This air is removed from thetubes and delivered to the return header I9, from which it may berelieved in any suitable manner.

Further to insure the elimination of air from the tubes, the orifice 28which is nearest the header I8 is spaced from the header at a greaterdistance than the distance between successive or adjacent orifices. Thisincreased distance results in the formation of a relatively low pressurein the return tube near the return header, due to the greater cooling ofthe steam, and this lower pressure causes air to flow toward the headerfrom all parts of the tubes. Removing air from the tubes of the heaterrenders all of the heat transfer service available for effective heattransfer, so that highly efficient operation of the heater is obtained.

To prevent bypassingair around the heater tubes, the outer casing ispreferably provided with baffles 30 and 3|, located, respectively, atthe top and bottom of the casing structure and extending substantiallycompletely thereacross.

To facilitate fabrication of the apparatus, the header structure I6 ispreferably provided with a plurality of solder channels 32, adapted toprovide communication between the exterior of the header structure and aplurality of annular solder grooves 33 formed in the partition I'Ia, oneof such grooves extending around each tube 22 introduced withinpartition I'Ia. In this manner the tubes 22 may be soldered to partitionIIa with great facility. Similarly, solder holes 34 formed in headerextension 24 communicate with solder grooves 35 extending around eachouter tube 23, so that these tubes also may readily be soldered to theheader structure.

In air heaters heretofore known, much difllculty has been experienceddue to freezing of condensate because of the low temperature of the airpassed into contact with the heater. The construction herein described,however, renders freezing of condensate virtually impossible. It will beappreciated that all condensate returning to the header I9 through tubes23 'is in heat exchange relation with steam being supplied within tubes22. Further, since the outer tubes are thermally bonded to the headerstructure I6 and hence to the steam supply header ill, the outer tubesare heated by the steam contained within the supply header. The factthat the outer tubes are thus heated further tends to prevent thetemperature of the condensate from falling below the freezing point.Again, the condensate within header I9 is heated by steam in the headerI8, this heat being transmitted through partition Ma. The condensate inheader I9 is also heated by heat transmitted through the outer walls ofthe header structure from steam in supply header I8. Thus, freezing ofcondensate is prevented in both the tubes and in the return header, sothat at all times during operation of the apparatus unimpeded flow ofsteam and condensate therethrough is maintained.

If it is desired to throttle the supply of steam to the heater, in orderto reduce the heating effeet on the air passing therethrough, this maybe done without danger of freezing. Thus, if the pressure at which steamis supplied is reduced to such a point that steam is contained within,for example, only half of the length of the inner tubes, all of thereturning condensate will still be in good heat exchange relation withthe steam being supplied within the inner tubes, and freezing will beeffectively prevented as above indicated. The remaining portions of thetubes, under such operating conditions, will be inert and inactive, butthis fact in no way interferes with the free and continuous circulationof steam and condensate through the apparatus.

Moreover, the supply of steam may be throttled very considerably withoutafiecting the substantially even heating of air throughout all portionsof the heater.

The provision of the discharge or nozzle formations 29 serve tofacilitate the return of condensate to return header I9.

While a single bank of heating elements has been illustrated it will beunderstood that any lid Jim

till

aeaaoaa desired number of banks may be provided. Also, while it ispreferred to have but a single steam tube it within each outer tube it,two or more steam tubes may be provided Within each outer tube, ifdesired.

To insure effective contact between the air being heated and the fins Hof the heat exchanger, there preferably are provided V-shaped baffles itat the air outlet side of the heat exchanger, one of these baffles beingnested between and in contact with each pair of finned tubes. Suchlocation of the baffles routes the air in contact with the fins in adevious course and hence for a longer time. and thus increases the rateof heat transfer.

Fig. 4 illustrates a modified form of the invention which embodies thesame basic design as described above. However, it will be observed thatin this embodiment of the invention, the solder channels 32 and thesolder holes 3d are eliminated. To effect desired soldering of the tubes22 and 23, the solder grooves 330 and 35a are prefilled with suitablesoldering material, and after the tubes have been inserted in desiredposition heat is applied, as by means of a gas torch or the like, tomelt the solder and efi'ect the desired soldering of the tubes withinthe header structure.

In Fig. 4 the orifices 29a, through which steam is discharged from theinner tubes 22, are distributed along and around the tubes 22 as abovedescribed. However, in this embodiment, the directional nozzleformations are dispensed with. To provide for maintained concentricspacing of the tubes 22 within the tubes 23, there are provided aplurality of spacers 31. These spacers may comprise short lengths ofcopper wire or the like, preferably soldered or otherwise firmly securedto the inner tubes 22 and extending axially therealong. Preferably aspacer 31 is positioned diametrically opposite each orifice 29a, toinsure minimum interference with the flow of steam and condensate.

If desired, the spacers may be eliminated by "bumping out the tube atdiii'erent points, the bumps thus formed serving to maintain the desiredspaced relationship of the tubes.

If desired, a suitable strainer or filter may be provided in connectionwith the steam inlet to prevent particles of boiler scale and otherforeign matter from entering the tubes. Such a filter is indicated at itin Fig. i, and is preferably of the type which may be snapped into andout of desired position at the steam inlet connection ill.

Since many changes may be made in the invention without departing fromits scope, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense, applicant limiting himselfonly as indicated in the appended claims.

I claim:

1. A heating apparatus comprising a header structure, means forsupplying steam to an inlet portion of the header structure and forremoving steam and condensate from an outlet portion thereof, steamdistributing tubes connectedto said inlet portion of the headerstructure, steam and condensate return tubes surrounding each of saiddistributing tubes and connected to said outlet portion, saiddistributing and return tubes being closed at their ends remote from theheader structure, said distributing tubes having perfora-= tions spacedsubstantially throughout the lengththereof, said tubes being inclined sothat condensate from steam supplied to a portion of the distributingtubes will flow. back to the header structure and not proceed in adirection from the,

header structure beyond the points where condensation occurs in thetubes.

2. A heating apparatus comprising a header structure, means forsupplying steam to an inlet portion of the header structure and forremoving steam and condensate from an outlet portion thereof, steamdistributing tubes connected to said inlet portion of the headerstructure, steam and condensate return tubes surrounding each of saiddistributing tubes and connected to said outlet portion, said returntubes being closed at their ends remote from the header structure, saiddistributing tubes having perforations spaced substantially throughoutthe length thereof, said tubes being inclined so that condensate fromsteam supplied to a portion of the distributing tubes will flow back tothe header structure and not proceed in a direction from the headerstructure beyond the points where condensation occurs in the tubes.

CARLYLE M. ASHLEY.

